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Environmental coating problems
Environmental problems
Coating
by Ron Joseph
HVLP GOES MICRO Earlier this week I had the privilege of visiting Northrup Grumman in Hawthorne, Calif., to witness the application of a high-solids epoxy primer and polyurethane topcoat by means of their patent-pending Microsprayer. Jorge Millan and Arnold Comproni, coating application specialists at the company, have designed a micro spray head that can fit on the end of an HVLP spray gun. Well, it’s not quite that simple. Bill Smith of Air Verter has adapted the head of his HVLP gun to accommodate the Microsprayer, by no means an easy design job. Essentially, three very small diameter plastic hoses (for fluid, atomizing air, and fan air, respectively) are fed from the head of the HVLP gun, through an aluminum gun extension and corrugated flexible plastic tube to a micro orifice that fits at the end of the plastic tube. The orifice and cap are only 3/X in. in diameter. The key to this innovation is the corrugated flexible hose and the ability to rotate the head through 360”. When the trigger on the HVLP gun is activated a very soft spray fan less than 2 inches wide can be achieved. The purpose of the unique flexible hose is to allow the operator to get the orifice into narrow, otherwise inaccessible, areas such as between wiring harnesses in small aircraft compartments. Much like a fiber optic cable can be articulated and contorted to illuminate an area out of the line-of-site, the corrugated flexible tube of the Microsprayer allows painters to apply coatings into otherwise inaccessible areas. Previously, the operators used a conventional HVLP spray gun to do the same job, but overspray would fly in all directions and settle on surfaces that were not intended to be coated. With this new design operators can accomplish the same task with almost no overspray at METAL
FINISHING
l
JULY 1998
all. In fact, when I watched the demonstration, l was wearing a sports jacket and tie and stood within two feet of the operator. Needless to say when the demonstration was over my tie showed no tell-tale signs of’ a paint shop. I was truly amazed. Jorge Milan took a few 2-in. X 2-in. metal pieces and showed me how he could coat them with a high-solids. high-gloss white polyurethane topcoat, and yet maintain the high-gloss finish without compromising finish quality-no runs or sags, essentially no overspray. and most remarkably a transfer efficiency of over 8096. Under normal conditions the same application with a conventional HVLP gun would probably yield a transfer efficiency less than IO%! Northrup Grumman is using this device to prime and sometimes also topcoat small compartments on their F18 assembly line where assembly operators do not want to be interrupted while the painters are doing their .job. For your interest, Northrup Grumman has licensed their technology to Air Verter, and I foresee numerous aircraft and general commercial applications for this remarkable little device. You might ask what the downside is? My guess is that if one wants to maintain the high transfer efficiency that I witnessed, the coating delivery rate will be limited. In other words based solely on what I saw, the current design might not be suitable for fast moving production lines where high fluid flow rates are required: however. I don‘t want to prejudge this important new tool. nor underestimate the ingenuity of the designers. With some gentle arm twisting I managed to encourage Arnold Comproni to submit a paper on this technology. which we hope to publish within the next few months. In addition I plan to use this device in some aircraft paint application tests later this 0 Copyright
Elsevier
Science
Inc.
year and will report back to you on my findings.
CAPTURING OVERSPRAY FROM TOUCH-UP OPERATIONS Not satisfied with only one invention the Northrup Grumman engineers have also designed a device, which they have named Portable Air Pollution Control Equipment (PAPCE, pronounced Pap-See). This wonderful device operates much like a portable spray booth; however, it is intended solely for touch-up type operations, which are performed outside a conventional spray booth. This is particularly valuable to prevent the emissions of particulates. such as chromate-containing overspray, from entering work areas where the workforce would otherwise be subjected to inhalation of these contaminants. The machine has two cone-shaped hoods that are connected via flexible ducting to a large portable metal box. Inside the box are primary and secondary spray filters, a carbon adsorption filter, and a HEPA filter. Ail is vacuumed from the hoods into the device and the overspray is collected onto the filter surfaces. Although the carbon adsorption filter is not claimed to be totally effective in abating VOC emissions, apparently it does have an effect on reducing the emissions. According to Arnold Comproni, the PAPCE is used on the F18 assembly line where the Microsprayer applies the chromate-containing primer into the difficult-to-reach areas that I described earlier. Without such a device the company would have had great difficulty getting permission from the South Coast AQMD to apply the primer outside a spray booth. With the PAPCE this problem is solved. Having seen the unit I can see applications nof only for touch-up oper31
ations outside a spray booth but also for some specific applications inside an existing booth. In particular I believe it could be used in situations where a chromate-containing primer needs to be applied to small exposed metal surfaces. For instance, many aerospace facilities spot prime exposed rivets and other small areas that have been scuff sanded to bear metal. For the most part an HVLP cup gun is used to apply the primer, and the overspray finds its w’ay to the dry filter bank inside the large spray booth. When it comes time to change the filters they must be disposed of as hazardous waste, but since some of these booths are huge (hangars. in fact) the disposal costs are exorbitant. It is possible that with a device such as the PAPCE spot priming can be carried out, and the overspray can be captured on only three small filters. Even though they will eventually need to be disposed of as hazardous waste, three is a lot less than tens, as in the case of a spray booth hangar. This equipment is not intended to replace spray booths. It is intended solely for the application of very small amounts of coating and the capture of small amounts of overspray. With the kind cooperation of Milan. Comproni, and Smith. in the near future I plan to evaluate this equipment for its practicability at an Air Force
base where an FlS will be repainted. In any case I’ll report back to you with my findings. EPA CLARIFIES OF HVLP
In its original version of the Aerospace MACT Standard the EPA defined HVLP spray equipment as one that operates with an atomizing air pressure less than 10.0 psig at the cap and ;I fluid pressure not exceeding 100 psig. By limiting the fluid pressure to 100 psig the EPA essentially disapproved the use of airless and air-assisted airless spray equipment, both of which deliver fluid at pressures well in excess OF 100 psig. In Fcdc~rd Re,qisteK Vol 63, No 59, page 15009. of March 27. 199X, the EPA dropped the fluid pressure limitation in its definition. In doing so they opened the door to a few air-assisted airless spray guns that have been designed so that the air pressure used to shape the spray fan does not exceed IO.0 psig. Already several years ago the South Coast AQMD made a similar change to ils definition of HVLP, but it is only as of the March 27 date that the EPA followed suit. This means that spray guns such as the Rinks Mach 2 gun, to name only one of several. can be used under this definition. We should applaud the EPA for this move.
High-performance, Chromate-free conversion coatings for Aluminum NATURAL COATING SYSTEMS, LLC l l l l
Superior Paint Adhesion Superior Corrosion Resistance Aqueous “Drop-In” Stages, No VOCs Processes are Very Cost Competitive
----. .. . .-....--.-.-.. . ^ -... No &-rosion in Over 1000 Hours in _-_-~ ASTM B-I I7 _---.- ---------Phone: 765-288-9990 Fax: 765-288-9991 Or visit us at: www.ncsllc.com Circle
METAL FINISHING
035 on reader l
information
JULY 1998
DEFINITION
as there is a definite need for air-assisted airless guns in the industrial coatings application market. Some words of caution: (1) Before you assume that these specially designed air-assisted airless guns comply with the definition of HVLP I urge you to first read the definition published in your local or state regulation. For instance, not all of the air pollution districts in California have dropped the fluid pressure limit. (2) May I suggest that before rushing to use air-assisted airless guns. you are advised to first determine whether or not they are appropriate for your application. Typically, they can atomize much higher fluid flow rates than can the conventional HVLP guns, but be careful that you do not deposit more paint than you need. (3) While these guns are wonderful for coating medium and large sized parts. they arc‘ often an over-kill for the painting of small parts where it might be difficult to control your film build. (4) Not all air-assisted airless guns comply with the 10.0 psig limit, and you should first confirm this with your equipment vendor. (5) Finally, the rrgulation still requires that you confirm that the atomizing air pressure at the cap of the gun does not exceed 10.0 psig. Ron conxultnnt
Joseph is an in Saratoga.
independent coating Calif. MF
GUARANTEED BEST IN OUR CLASS
Heay Duty BenchTop Vibratoy Mill Equipment l
The Most Powerful I Cubic Foot... 1HP Finishel On-the-Market...‘Todav! 1 Year warranty
l
Free 10 day trial period.
NOVA FINLSHINVC SYSTEMS’INC’. P 0. Box I85 l Hatboro, I 6 IO Republic Rd. l Huntqdon Ph 215-942-4474
l
BOO-444-41590
PA 19040 Valley, PA I9006 Fa~215-953-1342
card
33
Coating
by Ron Joseph
HVLP GOES MICRO Earlier this week I had the privilege of visiting Northrup Grumman in Hawthorne, Calif., to witness the application of a high-solids epoxy primer and polyurethane topcoat by means of their patent-pending Microsprayer. Jorge Millan and Arnold Comproni, coating application specialists at the company, have designed a micro spray head that can fit on the end of an HVLP spray gun. Well, it’s not quite that simple. Bill Smith of Air Verter has adapted the head of his HVLP gun to accommodate the Microsprayer, by no means an easy design job. Essentially, three very small diameter plastic hoses (for fluid, atomizing air, and fan air, respectively) are fed from the head of the HVLP gun, through an aluminum gun extension and corrugated flexible plastic tube to a micro orifice that fits at the end of the plastic tube. The orifice and cap are only 3/X in. in diameter. The key to this innovation is the corrugated flexible hose and the ability to rotate the head through 360”. When the trigger on the HVLP gun is activated a very soft spray fan less than 2 inches wide can be achieved. The purpose of the unique flexible hose is to allow the operator to get the orifice into narrow, otherwise inaccessible, areas such as between wiring harnesses in small aircraft compartments. Much like a fiber optic cable can be articulated and contorted to illuminate an area out of the line-of-site, the corrugated flexible tube of the Microsprayer allows painters to apply coatings into otherwise inaccessible areas. Previously, the operators used a conventional HVLP spray gun to do the same job, but overspray would fly in all directions and settle on surfaces that were not intended to be coated. With this new design operators can accomplish the same task with almost no overspray at METAL
FINISHING
l
JULY 1998
all. In fact, when I watched the demonstration, l was wearing a sports jacket and tie and stood within two feet of the operator. Needless to say when the demonstration was over my tie showed no tell-tale signs of’ a paint shop. I was truly amazed. Jorge Milan took a few 2-in. X 2-in. metal pieces and showed me how he could coat them with a high-solids. high-gloss white polyurethane topcoat, and yet maintain the high-gloss finish without compromising finish quality-no runs or sags, essentially no overspray. and most remarkably a transfer efficiency of over 8096. Under normal conditions the same application with a conventional HVLP gun would probably yield a transfer efficiency less than IO%! Northrup Grumman is using this device to prime and sometimes also topcoat small compartments on their F18 assembly line where assembly operators do not want to be interrupted while the painters are doing their .job. For your interest, Northrup Grumman has licensed their technology to Air Verter, and I foresee numerous aircraft and general commercial applications for this remarkable little device. You might ask what the downside is? My guess is that if one wants to maintain the high transfer efficiency that I witnessed, the coating delivery rate will be limited. In other words based solely on what I saw, the current design might not be suitable for fast moving production lines where high fluid flow rates are required: however. I don‘t want to prejudge this important new tool. nor underestimate the ingenuity of the designers. With some gentle arm twisting I managed to encourage Arnold Comproni to submit a paper on this technology. which we hope to publish within the next few months. In addition I plan to use this device in some aircraft paint application tests later this 0 Copyright
Elsevier
Science
Inc.
year and will report back to you on my findings.
CAPTURING OVERSPRAY FROM TOUCH-UP OPERATIONS Not satisfied with only one invention the Northrup Grumman engineers have also designed a device, which they have named Portable Air Pollution Control Equipment (PAPCE, pronounced Pap-See). This wonderful device operates much like a portable spray booth; however, it is intended solely for touch-up type operations, which are performed outside a conventional spray booth. This is particularly valuable to prevent the emissions of particulates. such as chromate-containing overspray, from entering work areas where the workforce would otherwise be subjected to inhalation of these contaminants. The machine has two cone-shaped hoods that are connected via flexible ducting to a large portable metal box. Inside the box are primary and secondary spray filters, a carbon adsorption filter, and a HEPA filter. Ail is vacuumed from the hoods into the device and the overspray is collected onto the filter surfaces. Although the carbon adsorption filter is not claimed to be totally effective in abating VOC emissions, apparently it does have an effect on reducing the emissions. According to Arnold Comproni, the PAPCE is used on the F18 assembly line where the Microsprayer applies the chromate-containing primer into the difficult-to-reach areas that I described earlier. Without such a device the company would have had great difficulty getting permission from the South Coast AQMD to apply the primer outside a spray booth. With the PAPCE this problem is solved. Having seen the unit I can see applications nof only for touch-up oper31
ations outside a spray booth but also for some specific applications inside an existing booth. In particular I believe it could be used in situations where a chromate-containing primer needs to be applied to small exposed metal surfaces. For instance, many aerospace facilities spot prime exposed rivets and other small areas that have been scuff sanded to bear metal. For the most part an HVLP cup gun is used to apply the primer, and the overspray finds its w’ay to the dry filter bank inside the large spray booth. When it comes time to change the filters they must be disposed of as hazardous waste, but since some of these booths are huge (hangars. in fact) the disposal costs are exorbitant. It is possible that with a device such as the PAPCE spot priming can be carried out, and the overspray can be captured on only three small filters. Even though they will eventually need to be disposed of as hazardous waste, three is a lot less than tens, as in the case of a spray booth hangar. This equipment is not intended to replace spray booths. It is intended solely for the application of very small amounts of coating and the capture of small amounts of overspray. With the kind cooperation of Milan. Comproni, and Smith. in the near future I plan to evaluate this equipment for its practicability at an Air Force
base where an FlS will be repainted. In any case I’ll report back to you with my findings. EPA CLARIFIES OF HVLP
In its original version of the Aerospace MACT Standard the EPA defined HVLP spray equipment as one that operates with an atomizing air pressure less than 10.0 psig at the cap and ;I fluid pressure not exceeding 100 psig. By limiting the fluid pressure to 100 psig the EPA essentially disapproved the use of airless and air-assisted airless spray equipment, both of which deliver fluid at pressures well in excess OF 100 psig. In Fcdc~rd Re,qisteK Vol 63, No 59, page 15009. of March 27. 199X, the EPA dropped the fluid pressure limitation in its definition. In doing so they opened the door to a few air-assisted airless spray guns that have been designed so that the air pressure used to shape the spray fan does not exceed IO.0 psig. Already several years ago the South Coast AQMD made a similar change to ils definition of HVLP, but it is only as of the March 27 date that the EPA followed suit. This means that spray guns such as the Rinks Mach 2 gun, to name only one of several. can be used under this definition. We should applaud the EPA for this move.
High-performance, Chromate-free conversion coatings for Aluminum NATURAL COATING SYSTEMS, LLC l l l l
Superior Paint Adhesion Superior Corrosion Resistance Aqueous “Drop-In” Stages, No VOCs Processes are Very Cost Competitive
----. .. . .-....--.-.-.. . ^ -... No &-rosion in Over 1000 Hours in _-_-~ ASTM B-I I7 _---.- ---------Phone: 765-288-9990 Fax: 765-288-9991 Or visit us at: www.ncsllc.com Circle
METAL FINISHING
035 on reader l
information
JULY 1998
DEFINITION
as there is a definite need for air-assisted airless guns in the industrial coatings application market. Some words of caution: (1) Before you assume that these specially designed air-assisted airless guns comply with the definition of HVLP I urge you to first read the definition published in your local or state regulation. For instance, not all of the air pollution districts in California have dropped the fluid pressure limit. (2) May I suggest that before rushing to use air-assisted airless guns. you are advised to first determine whether or not they are appropriate for your application. Typically, they can atomize much higher fluid flow rates than can the conventional HVLP guns, but be careful that you do not deposit more paint than you need. (3) While these guns are wonderful for coating medium and large sized parts. they arc‘ often an over-kill for the painting of small parts where it might be difficult to control your film build. (4) Not all air-assisted airless guns comply with the 10.0 psig limit, and you should first confirm this with your equipment vendor. (5) Finally, the rrgulation still requires that you confirm that the atomizing air pressure at the cap of the gun does not exceed 10.0 psig. Ron conxultnnt
Joseph is an in Saratoga.
independent coating Calif. MF
GUARANTEED BEST IN OUR CLASS
Heay Duty BenchTop Vibratoy Mill Equipment l
The Most Powerful I Cubic Foot... 1HP Finishel On-the-Market...‘Todav! 1 Year warranty
l
Free 10 day trial period.
NOVA FINLSHINVC SYSTEMS’INC’. P 0. Box I85 l Hatboro, I 6 IO Republic Rd. l Huntqdon Ph 215-942-4474
l
BOO-444-41590
PA 19040 Valley, PA I9006 Fa~215-953-1342
card
33